1. Field of the Invention
The present invention relates to a microwave and luminous probe to be used in a system for detecting the piston position and the light emitted in a combustion chamber of an internal combustion engine on the basis of a microwave signal and a luminous signal.
2. Description of the Prior Art
Several examples of probes to be used in the above system have been proposed, but problems have been encountered in practical use such as a complicated structure and difficulty in reduction in size due to the large dielectric constant of a dielectric material.
Namely, (1) it has been difficult to give a small diameter to the tip end of a probe, (2) it has also been difficult to machine a dielectric material because the coaxial line (annular passage) is made solid, and (3) an internal conductor must be hollowed to transmit the light therethrough and must have a thickness to enable detection of the light.